Field of the Invention
The present invention relates to a one-wheel-failure vehicle control device for a four-wheel independent drive vehicle which device performs a vehicle motion control when one wheel of a four-wheel independent drive vehicle equipped with an in-wheel motor or the like has failed.
Description of Related Art
As a vehicle control method employed when one of the drive sources of a vehicle that independently drives left and right wheels has failed and can no longer generate a normal braking/driving force, the following manners have been proposed.
According to Patent Document 1, when one of the drive sources has become inoperable during turning in a front-wheel drive vehicle that independently drives left and right wheels, the driving force is controlled by the following methods to suppress behavior change of the vehicle, thereby improving a running stability of the vehicle.
a) When the drive source of the front wheel on an outer wheel side on turning has become inoperable, the driving force for the front wheel on an inner wheel side on turning located on the opposite side thereof is gradually reduced such that the driving force becomes zero after an elapse of a predetermined period of time.
b) When the drive source of the front wheel on the inner wheel side on turning has become inoperable, a supply of the driving force to the front wheel on the outer wheel side on turning located on the opposite side thereof is immediately stopped.
According to Patent Document 2, when the drive source of one wheel of a four-wheel independent drive vehicle has failed, the braking/driving force on a laterally opposite side of a failed wheel is approximated to the braking/driving force of the failed wheel. The degree of the approximation of the braking/driving force is changed in accordance with a state of failure in the following methods.
a) For a vehicle in which the front wheels have a positive kingpin offset, when one of the front wheels (turnable wheels) has failed, the degree of approximation of the braking/driving force is set to be higher than in the case where one of the rear wheels (non-turnable wheels) has failed.
b) For a vehicle in which the front wheels have a negative kingpin offset, when one of the front wheels (turnable wheels) has failed, the degree of approximation of the braking/driving force is set to be lower than that in the case where one of the rear wheels (non-turnable wheels) has failed.
c) The greater the difference in braking/driving force between the left and right wheels in the event of failure is, the higher the degree of the approximation of the braking/driving forces is set to be.
According to Non-Patent Document 1, when a motor for one wheel of an eight-wheel independent drive vehicle has failed, the following methods are taken in accordance with a failure mode.
a) When the motor is freed: a motor located on the laterally opposite side of a failed motor is freed.
b) When the motor is locked: a regenerative braking force is generated by the motor located on the laterally opposite side of the failed motor.